almost finished transferring BST to AVL using geeksforgeeks AVL insert and delete algorithms

program3/AVLCommands.cpp

@@ -14,13 +14,15 @@ BSTNode::BSTNode(int key) :
 	key_(key),
 	parent_(std::weak_ptr<BSTNode>()),
 	left_(nullptr),
-	right_(nullptr) {} // add a height_
+	right_(nullptr),
+	height_(1) {} // add a height_
 
 BSTNode::BSTNode(int key, std::weak_ptr<BSTNode> parent) :
 	key_(key),
 	parent_(parent),
 	left_(nullptr),
-	right_(nullptr) {}
+	right_(nullptr),
+	height_(1) {}
 
 bool BSTNode::IsLeaf() const {
 	return left_ == nullptr && right_ == nullptr;
@@ -203,6 +205,7 @@ void AVLCommands::Insert(int key) {
 }
 
 bool AVLCommands::Delete(int key) {
+	// base BST delete
 	std::shared_ptr<BSTNode> currentNode = root_;
 	while (currentNode != nullptr) {
 		if (currentNode->key_ == key) {
@@ -225,6 +228,33 @@ bool AVLCommands::Delete(int key) {
 		currentNode = (key < currentNode->key_) ?
 			currentNode->left_ : currentNode->right_;
 	}
+
+	// update height of current node
+	currentNode->height_ = 1 + max(height(currentNode->left_), height(currentNode->right_));
+
+	// Update balance factor of this ancestor's node
+	int currentNodeBalance = getBalance(currentNode);
+
+	// Check if unbalanced
+	// Left Left Case
+  if (currentNodeBalance > 1 && getBalance(currentNode->left_) >= 0)
+      rightRotate(currentNode);
+
+  // Right Right Case
+  if (currentNodeBalance < -1 && getBalance(currentNode->right_) <= 0)
+      leftRotate(currentNode);
+
+  // Left Right Case
+  if (currentNodeBalance > 1 && getBalance(currentNode->left_) < 0) {
+      currentNode->left_ =  leftRotate(currentNode->left_);
+      rightRotate(currentNode);
+  }
+
+  // Right Left Case
+  if (currentNodeBalance < -1 && getBalance(currentNode->right_) > 0) {
+      currentNode->right_ = rightRotate(currentNode->right_);
+      leftRotate(currentNode);
+  }
 	return false;
 }
 

program3/AVLCommands.h

@@ -20,10 +20,10 @@ class BSTNode {
 
  private:
   int key_;
-  int height_;
   std::weak_ptr<BSTNode> parent_;
   std::shared_ptr<BSTNode> left_;
   std::shared_ptr<BSTNode> right_;
+  int height_;
 
   //friend BST;
   friend AVLCommands;
@@ -46,13 +46,13 @@ class AVLCommands {
   int getRight(int key);
 
  private:
-   int max(int a, int b);
-   int height(std::shared_ptr<BSTNode> currentNode);
-   int getBalance(std::shared_ptr<BSTNode> currentNode);
-   std::shared_ptr<BSTNode> rightRotate(std::shared_ptr<BSTNode>);
-   std::shared_ptr<BSTNode> leftRotate(std::shared_ptr<BSTNode>);
-   void DeleteLeaf(std::shared_ptr<BSTNode> currentNode);
-   int DeleteMin(std::shared_ptr<BSTNode> currentNode);
+  int max(int a, int b);
+  int height(std::shared_ptr<BSTNode> currentNode);
+  int getBalance(std::shared_ptr<BSTNode> currentNode);
+  std::shared_ptr<BSTNode> rightRotate(std::shared_ptr<BSTNode>);
+  std::shared_ptr<BSTNode> leftRotate(std::shared_ptr<BSTNode>);
+  void DeleteLeaf(std::shared_ptr<BSTNode> currentNode);
+  int DeleteMin(std::shared_ptr<BSTNode> currentNode);
 
  	std::shared_ptr<BSTNode> root_;
  	size_t size_;